LENS-CAL I. Barabanov, V. Gurentsov, V. Kornoukhov Institute for Nuclear Research, Moscow and R. S. Raghavan, Virginia Tech LONU-LENS Blacksburg, Oct 15, 2006

The Capture Cross Section is σ = x10-44 x [g A 2 B(GT)] W e p e F(ZW)] g A 2 = 1.58 W e Prompt Electron energy in mc 2 units p e Electron momentum = √ (W e 2 – 1) F(Z=50, W e ) Fermi function B(GT) is reduced Gamow Teller Nuclear Matrix Element B(GT) must be calculated/ measured in Laboratory Theoretical Estimate made in RSR original PRL paper: Using nuclear systematics and shell model parameters of the The In (initial) and Sn (final) states: B(GT) ~ 0.16 : Nuclear Matrix Element for Indium Neutrino Capture Reaction

Measurement: J. Rapaport et al, Phys.Rev. Letters 54, 2325 (1985) Performed via 115 In(p,n) forward scattering at Indiana U Cyclotron σ (p,n) is proportional to B(GT) Forward (0 o) neutron emission with. E p = 120 MeV and 200 MeV B calibrated against B(F)= 3 for Analog state Result: B(GT) (neutrino state) = 0.17 (10%) B(GT) ~0 to states upto 4 MeV V. good agreement with rsr theory Neutrino state In-Sn neutrino state

In(p,n) reaction is strong interaction reaction which measures B(GT) via strong interactions. Desirable to have direct weak interaction measurement of B(GT)  Direct measurement using a megCuri neutrino source.  LENS-CAL  Source Technology & Expertise developed in Russia (SAGE detector calibration with 51 Cr and 37 Ar Sources)  LENS-CAL  MegaCurie source made in Russia + Compact In loaded detector Operated probably in Baksan Neutrino Source Calibration of B(GT)

SourceDecayMode /Produced by  E   keV) E e = E  keV Background 37 Ar Haxton EC/ (n,  50.5 d814(100%)700Int. Bremms ; ~  5x10 -4 h /decay 51 Cr RSR Kuzmin EC/ (n,  ) 40.1 d751 (90%)  (10%) Imp.  ’s (MeV) %?? 65 Zn Louis Alvarez EC(  + )/ (n,  ) 353 d1350 (50%)  511  (2%); Imp.  ’s. Table I: Characteristics of neutrino Sources for LENS-CAL Neutrino Energy typically 700 keV

Source Energy ~700 keV OK for LENS-CAL First: No other excited state reached. LENS tag ensures excitation of specific state in daughter Sn. Usual problem in radiochem expts such Ga is not present here Second: Energy beyond In beta Endpoint. So double Coincidence enough Simplified tag analysis

Design Concepts for LENS-Cal Detector Indium Density Consider a neutrino source in the center of a spherical detector The event yield Y is: Y= σ ε ρ  { S /(4π r2 )} k 4π r 2 dr = σ ε k ρ R(= radius of detector) -k = the fraction of 4π enclosed by the detector array (k ≤1) ε = the signal detection efficiency  In foil thickness  Y varies as ρ the Indium Density.  Need design with high Indium density  In LS typically In is 8% -15%  Can this be increased?  In foil –Plastic Sandwich Stack Detector

Basic Idea of Sandwich Stack -- Use thin Indium foil sandwiched by thin plastic bar Thicknesses: Indium foil  Signal electron emerge with high efficiency Plastic  thickness > range of electron Optimized thicknesses: In foil mg/cm 2 Plastic: 300 mg/cm 2 Good for E ν ~700 keV

In Sandwich Stack Expts Bell Labs 1979 Original Intent –pp neutrinos !  very thin In foil <10mg/cm 2  plastic 160mg/cm 2  ρ~60g/l Compared to Ar source: In foil 100mg and Plastic 300 mg  ρ~330 g/l Sandwich stack design offers X2.2 higher Indium density Modules with Stacks 20x20x200cm Light attenuation OK Recent INR Monte Carlos Verify

LENS-CAL: Conceptual Design based on Sandwich Stack In Loading Ar Ar Plan view Side view Indium = 8 tons Plastic 25 tons. Indium 100mg/cm2 Plastic 300mg/cm2 Indium Density ρ = 0.33 g/cm3. Plastic Module 20x20x200 max Light guides/PMT’s

51Cr source with activity - 5 mCq Neutrino cross-section capture – 3.03x10-44 cm2 In thickness 0.1 g/cm2 Scintillator slab thickness 3 mm Threshold for neutrino electron – 450 keV Threshold of shower energy keV. Total In mass – 5 t Module cross section 5*5 cm2 10*10 cm2 15*15 cm2 Neutrino detection efficiency, % Background (total) per day Number of neutrino events per 100 d Good Event Rate and Low intrinsic In Bgd. Preliminary Simulation Results

[i] [i] LSND Collaboration, Phys. Rev.Lett. 79 (1998) 1774 [ii] [ii] KamLand Collaboration, Phys. Rev. Lett. 94 (2005) New Physics from LENS Cal? Look for Sterile Neutrino Oscillations in LENS-CAL L. Mikaelyan et al, hep-ph/ ; Jonathan Link LSND  Δm2 ~1eV 2 ~10 4 x Δm 12 2 of reactor ν e ̃ sin2 2θ ~0.1to  Test at short baselines <10m available in LENS-CAL  Kamland 10 5 m x10 -4 (0.7/3 MeV) ~ 2m in LENS-CAL  Look for event rate distribution vs. radius in LENS-CAL detector !

Conclusions Preliminary Analysis Shows Indium sandwich Stack Detectors with Technically feasible 51Cr sources are viable Further work for: other sources Source Strengths …. Revisit In LS modules  lower density but higher efficiency